Hygiene of water and water supplies / by Patrick Hehir.

Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Hygiene of water and water supplies / by Patrick Hehir. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    impurities to the water. The filtering medium should not be liable to clog; and lastly the delivery of the water should be reasonably lasting. The first of these conditions obviously sets aside all filters of the older, and what used to be the usual, pattern, where only a small layer of filtering material was present, which was cemented up, so as not to be reached without breaking open the apparatus. The second condition is fulfilled, so far as filter- ing power is concerned, by a number of media, chiefly spongy iron, magnetic oxide, or carbide of iron, and charcoal for a short time. Coke, sand, and some other substances arrest organisms for some time, but do not affect the organic constituents chemically. With regard to bulk of material, this is fairly well attended to in the filters where loose material is used; but where solid blocks are employed, the size is often quite incommensurate with the work they are called upon to do. The third condition is complied with by spongy iron, magnetic oxide, or carbide, and some other materials ; but (as before mentioned) not by animal charcoal in the loose condition. As solid blocks, it seems to yield less to water than in the granular condition. The fourth condition depends a good deal upon the relative degree of impurity of the water. The spongy iron, and the magnetic oxide or carbide on the whole, last the longest. The fifth condition demands that nothing organic shall be used in the construction of the filter, or in the packing of the interior. Iron or other material must be protected from the action of the water.